Method of making anisotropic permanent magnets



I June 3, 1958 K. J. DE VOS ET AL METHOD OF MAKING ANISOTROPIC PERMANENT MAGNETS Filed Jan. 18, 1956 ,l 1.2 l l I,

to n I I 10 as 20 2'5 30 as 40 INVENTOR KRIJN JACOBUS DE VOS ADO LF JOHANNES JACOBUS KOCH HENDRIK JOHANNES MEERKAMP VAN EMBDEN BARTHOLOMEUS HAE 8 11/ JOHANNES FLIPSE AGEKT United Krijn Jacobus de Vos, Adolf Johannus Jacobus Koch,

ice

of a magnet obtained by the usual cooling of at least 30 C./min. in said temperature range.

The aforesaid substantially constant temperature is obtainable by subjecting the alloys to the action 01f the Hendrik Johannes Meerkarnp Van Embden, Bartholo- 5 magnetic field, in a metal or salt bath of suitable temmellS and Johannes P Eiildhovell, Neihefperature or in an oven. In practice, said temperature f f y 1119511e asslgnmems, to North variation of less than 20 C. may occur in ovens since g fi New York a the temperature of these cannot be maintained at a l f f e aware strictly constant level. f f f 'x 1956 Sena] 559,982 -10 The alloy, after being quenched to a temperature of clalyms P y, application Netherlands January 1955 900 C., may be further cooled to room temperature Claims. (Cl. 148-103) and subsequently heated into the desired temperature Methods are known for making anisotropic perma range below the Curie-temperature for treatment in a nent magnets containing up to 42% of Co, to 20% 919511999 field- Alterflatlvely alloy m be cooled of Ni, 6% to 10% of Al, 2% to 8% of Cu, 4% to 10% rapidly from 900 1nto the deslred temperature range. of Ti and Fe, in order to secure ahigh coercivity H of After treatment 111 a magnet field: to room more than 900 oersteds and a .high (BH)max value, the temperature may be efiected by any iconvement means, alloys being cooled from a temperature of approximately Provlded 1t 15 not done too A normal annealing 1225 C. to a temperature of 600 C. in a magnetic treatIPePt x then follow thls treatmentfield at an average cooling rate of at least This 1nvent1on perrmts the manufacture of magnets in Q/mht With several of Such magnets the WhlCh said improvement of the (BI-I) value is at least coercivity is 1080 oersteds with a (BH) value of 1,000,000 g-oersteds- I 2,460,000 g. oersteds, 1140 oersteds with 3,500,000 g. The Process P lnvenflon 9 Parflcular advanoersteds and 925 oersteds with 4,100,000 g. oersteds retags when apphed to alloys contalmng more than spectively. Such magnets have the advantage that they 0 to 42% of can be used in constructions wherein strong demagnetiz- Should a predomlnfltlng crystal or1entat1o1 1 be des1red, ing fields prevail. This means that the magnet may have m Order to secure h l m l properties the melt avery small length. may be caused to solidlfy directionally by cooling slowly, The present invention is based on the discovery that for q P in an Oven in accordance with Dutch Patent the aforesaid magnets, when subjected to a particular if z bl heat-treatment while retaining a high coercivity in excess P t e owmg es S.evera1 .examples are glven of 900 oersteds and in the majority of cases even with tatmg the tune penods durmg which the alloys stayed an increase in coercivity, reach a considerably higher m the lemperature range of to 70 below (BHMEX Vahm the Curicei-temperature, the followmg heat treatment being emp oye In accordance w1th our lnvention, the aforesaid alloy, I which contains 15% to 42% of Co, after being quenched sphdlgcamn the alloys were quenched comfrom a temperature higher than about 1200 C to at least presse mm rqom tqmperature they were reheated to the temperature llsted 1n the tables and maintained about 900 1s mamtamed under the actlon of a on said temperature for the stated number of minutes j l a h Q F range offfmm about l to Subsequently, they were cooled and annealed at an aver- 70 elow t e urn-temperature or 2 to 30 minutes, age coohng rate vof approximately C/Sec. preferably for at least 4 to 15 m1nutes at a substantlally h fi t li states f each alloy the B the He and constant temperatute, varylng less than 20 C. In thlS the )max respectively or a mag et 0f the same manner a magnet is obtained having a (BH) value composition but cooled from more than 1200 C. to exceeding at least 700,000 g. oersteds the (BH) value about 600 C. at a rate of about 30 to C./min.

Table Curie Hardening Profit of 00 N1 Al Cu Tl tempera tempera- Min. B, Hg (BHMM (BIDMX ture in ture in X1041 X106 6,840 870 1.65 t 780 7,420 922 2.6 t 18 20 7 6 5 835 800 2 7, 580 960 2. 8 1 2 129- a "24'' 'i4' '8' '3' m "855" "825" "9' 8: 280 950 3135 "0:8 9,020 946 3.7

249 9st 7 8 l 815 5 6:900 11400 a: 05 L4 Two examples are now giveniof magnets having a preponderating crystal orientation. In this case directional solidification of the melt ensued by slow cooling of the liquid alloy in an oven having a temperature of 1500 C. till the alloy has solidified, the alloys subsequently being reheated and treated in the aforesaid manner.

Ni Al Cu Tl C. Min. Bt- Ha (Emma:

The accompanying diagram shows the (BH) value in accordance with the Co value for magnets of the same composition with 5% of Ti, the upper curve concerning alloys treated in accordance with the invention and the lower curve relating to alloys treated in accordance with the usual method, the improvement upon the (EH) value being clearly evidenced.

While we have described our invention in connection with specific embodiments and applications, other modifications thereof will be readily apparent to those skilled in this art without departing from the spiritand scope of the invention as defined in the appended claims.

What is claimed is:

1. In the manufacture of a permanent magnet, the steps of forming a body of a ferrous alloy containing about to 42% cobalt, about 10 to nickehabout 6 to 10% aluminium, about 2 to 8% copper, about 4 to 10% titanium and the balance principally iron, quenching said'body from a temperature exceeding about 1200" C. to a temperature of about 900 CL, and subjecting said body to the action of a magnetic field while said body is maintained at a substantially constant temperature varying less than about 20 C. in a range of about 10 to 70 varying less than about 20 C. in a range of about 10 to C. below its Curie temperature for about 4 to 15 minutes whereby an anisotropicpermanent magnet having a substantially increased (BI-U is obtained.

3. The process of claim 1 in which the alloy contains from more than 30% to 42% of C0.

4. The method of claim 1 in which the alloy is slowly caused to solidify to cause a predominant crystal orientation before being subjected to the magnetic field and constant temperature treatment.

5. A permanent magnet made by the process of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS Hansen Mar. 7, 1950 Ebeling Dec. 11, 1951 

1. IN THE MANUFACTURE OF A PERMANENT MAGNET, THE STEPS OF FORMING A BODY OF A FERROUS ALLOY CONTAINING ABOUT 15 TO 42% COBALT, ABOUT 10 TO 20% NICKEL, ABOUT 6 TO 10% ALUMINUM, ABOUT 2 TO 8% COPPER, ABOUT 4 TO 10% TITANIUM AND THE BALANCE PRINCIPALLY IRON, QUENCHING SAID BODY FROM A TEMPERATURE EXCEEDING ABOUT 1200*C. TO A TEMPERATURE OF ABOUT 900*C., AND SUBJECTING SAID BODY TO THE ACTION OF A MAGNETIC FIELD WHILE SAID BODY IS MAINTAINED AT A SUBSTANTIALLY CONSTANT TEMPERATURE VARYING LESS THAN ABOUT 20*C. IN RANGE OF ABOUT 10* TO 70* C. BELOW ITS CURIE TEMPERATURE FOR ABOUT 2 TO 30 MINUTES WHEREBY AN ANISOTROPIC PERMANENT MAGNET HAVING A SUBSTANTIALLY INCREASED (BH)MAX IS OBTAINED. 